Air China A20N at Singapore on Sep 10th 2023, engine fire, smoke in cabin, evacuation

Last Update: August 30, 2024 / 17:06:51 GMT/Zulu time

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Incident Facts

Date of incident
Sep 10, 2023

Classification
Accident

Airline
Air China

Flight number
CA-403

Aircraft Registration
B-305J

Aircraft Type
Airbus A320-200N

ICAO Type Designator
A20N

An Air China Airbus A320-200N, registration B-305J performing flight CA-403 from Chengdu (China) to Singapore (Singapore) with 146 passengers and 9 crew, was descending towards Singapore when the crew declared emergency reporting they had received a forward cargo hold as well as a lavatory smoke indication. Smoke developed in the cabin. The aircraft landed on Singapore's runway 20L and stopped on the runway. The aircraft was evacuated via all slides (including the left hand overwing slides). 9 people received minor injuries. Emergency services extinguished a left hand engine (PW1127G) fire.

The runway was closed for about 3 hours as result of the occurrence.

Singapore's Civil Aviation Authority reported there were 9 minor injuries due to smoke inhalation and abrasions during the evacuation.

On Sep 11th 2023 the airline reported based on preliminary investigation results that an engine mechanical failure preceeded the emergency landing, the crew handled the occurrence according to procedures, the passengers were cooperative during the evacuation.

Singapore's TSIB have opened an investigation into the occurrence.

On Aug 30th 2024 Singapore's TSIB released their final report concluding the probable causes of the occurrence were:

- The smoke in cabin and the left engine fire was caused by the front carbon seal fracture of the No. 3 bearing. This resulted in oil leaking from the bearing compartment to the hot zones of the engine, which led to smoke/fumes being formed, with a twofold consequence: smoke/fumes travelling to the aircraft cabin and cargo compartment through the bleed system, and a localised fire at the engine tailpipe.

- The engine manufacturer’s engine health monitoring system had failed to detect the carbon seal “nesting” before it deteriorated to an undesirable “nesting” state and eventual carbon seal fracture.

- The TCOD (Tower Coordinator) missed copying the MAYDAY declaration of the aircraft from the ACOD (Approach Coordinator) and did not relay the information to the ARFF. The ANSP (Air Navigation Service Provider) did not require its controllers to acknowledge messages among colleagues with a full read back.

- The flight crew accepted to land on the ANSP’s preferred runway probably to avoid prolonging the communication with the ATC.

- There was delay of about one minute in the activation of the ARFF as the RWC (Runway 20L Coordinator) was establishing whether the flight crew could vacate the runway and the communication from flight crew was unclear.

The TSIB analysed:

Cause of cabin smoke and engine fire

- Post-incident examination of the left engine revealed that a carbon seal in the No. 3 bearing compartment had fractured and no remnants of the carbon element was found on the carbon seal carrier. This suggests that the undesirable state of No. 3 bearing front carbon seal fracture had occurred. However, the investigation team could not determine at which moment of the flight the fracture happened.

- The No. 3 bearing front seal fracture resulted in oil leaking from the front of the No. 3 bearing compartment towards to the rear of the LPC, the HPC, and the turbine exhaust case. These areas were characterised by high temperatures, which caused the leaked oil to vaporise and generate oil fumes/smoke.

- The oil fumes/smoke generated were extracted from the HPC together with the bleed air. The contaminated bleed air flowed through the aircraft bleed air system resulting in smoke in the cabin, cargo compartment and avionics compartment.

- The leaked oil also travelled through the bore of the HPC shaft and through the Low Pressure Turbine (LPT) shaft to the LPT area. The fire observed at the rear of the engine had likely resulted from the contact between the leaked oil and the high temperature LPT.

- The WO assessed that the fire was minor and localised. Post-incident
examinations of the engine also confirmed that there were no signs of fire
beyond the engine core.

Engine health monitoring system

...

- Prior to the event flight, the main oil filter differential pressure in the left engine and the oil debris count appeared to have been normal. However, this incident suggests that the database of patterns used as reference for detecting the deteriorated state of the carbon seal had not been sufficient. The investigation team noted that the engine manufacturer has since the incident included additional patterns in the algorithm to enhance the algorithm’s detection capability.

ACOD-TCOD communication

- the ACOD relayed to the TCOD the announcement by the NAPP regarding the MAYDAY declaration and that the aircraft had smoke in the cockpit. According to the TCOD, she heard the ACOD mentioning about the “smoke in cockpit” emergency but she did not hear the mentioning of the MAYDAY declaration. She acknowledged the ACOD by mentioning only the “smoke in cockpit” emergency.

- The ANSP did not require the practice of formal readback among air traffic controllers when announcements were made or when messages were passed around. Some form of acknowledgement would suffice. Thus, when the TCOD acknowledged receipt of the “smoke in cockpit” message, the ACOD took this as the TCOD’s acknowledgement that her message had reached the TCOD and presumed that the full content of the message had also reached the TCOD.

Landing runway assignment

- The flight crew were informed by the NAPP at about 15:53 that their landing runway would be Runway 20R and they configured their aircraft accordingly. Following their MAYDAY declaration at about 15:59, the flight crew were asked twice by the IAPP if they could use Runway 20L.

- The ATC recording showed that the flight crew had clearly requested for Runway 20R. However, IAPP needed to check with the Tower Manager and told the flight crew to stand by. The Tower Manager again required the IAPP to seek confirmation from the flight crew that they could not perform an RNP approach for landing on Runway 20L. The IAPP queried the flight crew accordingly. The flight crew relented and decided to focus on the emergency rather than prolonging the communications. Nevertheless, had the flight crew insisted on Runway 20R, it is probable that ATC would accede to their request for landing on Runway 20R.

...

Communication between flight crew and ATC for ARFF assistance

-After the aircraft landed and came to a stop on the runway, the flight crew informed the RWC that they needed the fire service. The RWC was aware that the aircraft had an emergency. He observed that the aircraft appeared to be operating normally when it landed on the runway and gathered that the aircraft could conduct any troubleshooting on the taxiway after vacating the runway. He was also mindful that there were aircraft waiting at the holding point for departure at that time. In view of these, the RWC asked the flight crew if they were able to taxi out of the runway. The reply from the PM was “we are in vacate… we vacating the runway… runway air china four zero three”. This response from the flight crew was unclear to the RWC on whether they were able to vacate the runway and the RWC repeated his query to the flight crew. This time, the PM replied, “we cannot evac… vacate the runway” and this was understood by the RWC that the flight crew could not vacate the runway. The RWC then cleared the ARFF vehicles to enter the runway, about one minute after the request was made by the flight crew. The delay did not impact the situation as the fire was minor, not growing and contained in the left engine’s tailpipe.

...
Incident Facts

Date of incident
Sep 10, 2023

Classification
Accident

Airline
Air China

Flight number
CA-403

Aircraft Registration
B-305J

Aircraft Type
Airbus A320-200N

ICAO Type Designator
A20N

This article is published under license from Avherald.com. © of text by Avherald.com.
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